M.Tech. / The removal and recovery of heavy metals from effluents has been a subject of significant importance due the negative impact these toxic metals have on human health and the environment as a result of water and soil pollution. Precipitation is the mostly widely used wastewater treatment method because it is the most economical and easier to implement and operate on a large scale. However, traditional precipitation methods using lime, sulfides or hydroxides recover metals in the form of a sludge which is not reusable and has to be disposed in landfills creating a potential environmental hazard and resulting in loss of valuable minerals. The current focus in effluent treatment is now on the recovery and re-use of these heavy metals rather than removal and disposal. This study investigated the use of hydrazine as a reducing agent to remove and recover Ni2+, Cu2+, Co2+ and Fe2+ from effluent by reduction crystallization. In this process chemically reduced aqueous metal ions were plated on to a base substrate (nickel powder) with no electrical current required for deposition. A feasibility study was carried out to test the efficiency and find the optimum operating conditions for this method and generate an understanding of the chemical and particulate process occurring. The results obtained indicate that hydrazine is an effective reducing agent for removal and crystallization of Ni2+, Cu2+, Co2+ and Fe2+/ Fe3+ into their elemental states with nickel powder as a seeding material. Over 99 % of metals were removed from the effluent in all the systems (Ni-only, Ni-Cu, Ni-Fe and Ni-Fe). Breakage, aggregation and molecular growth were identified as the predominant mechanisms occurring during the reduction crystallization process in Ni-only, Ni-Cu, Ni- Co systems and there was evidence of nucleation in Ni-Fe solution. These finding were confirmed by analysing the scanning electron micrographs of the powder obtained. A nearly spherical structure powder with wide distribution in particle size and evidence of fragmentation was obtained in all the experimental runs. vii The residual concentrations obtained were far below the required limit for effluent discharge into sewer where 20 mg/L Ni, 20 mg/L Cu and 20 mg/L Fe and the total metal concentration of 50 mg/L for Fe, Cr, Cu, Ni, Zn and Cd is stipulated. Reduction crystallization using hydrazine as a reducing agent can be utilized for controlling environmental pollution and eliminating hazardous metals from the environment.

En konceptlösning för ett elektrovinningssystem utvecklas baserat på Glenngårds (2019) tidigare arbete. Arbetet är genomfört så att det besvarar tre frågor om en potentiell konceptlösning. Frågeställningarna inkluderar vilka krav som behöver uppfyllas, design av en passande arkitektur och hur vissa konceptparametrar kan verifieras. Krav formuleras i huvudsak baserat på Glenngårds parametrar; säkerhet, kvalitet, användarvänlighet, enkelhet att tillverka, montera, underhålla systemet, kostnadseffektivitet och användning av standardiserade komponenter. Konceptet som genereras är baserat på att använda en elektrolytbehållare kring vilken andra system är fästa eller indränkta. Designen tillåter en grad av automatisering. En bruksprocess för konceptet beskrivs, relevanta komponenter förklaras och vidare utveckling föreslås. En lista med föreslagna tester för verifikation med hjälp av prototypen är också given. / A concept solution for an electro winning system is developed based on the previous work done by Glenngård (2019). This project is made to answer three questions about a potential concept solution, including what requirements need to be fulfilled, design of a suitable architecture and how to verify certain parameters of the concept. Requirements are formulated mainly based on Glenngård’s parameters; safety, quality requirements, ease of use, ease of manufacturing, ease of assembly, ease of maintenance, cost efficiency and use of standardized components. The concept that is generated is based on a single electrolyte container around which surrounding systems are attached or immersed. The design allows a degree of automatization. A process of use is described, relevant components are explained, and further developments are suggested. A list of suggested tests to be carried out for verification using a prototype is also provided.

This report explores simultaneous crystallization in multicomponent solutions to intensification of metal recovery in lithium-ion batteries. The main focus is to evaluate and compare the efficiency of sodium hydroxide and sodium carbonate as precipitating agents in recovering cobalt, nickel, manganese and lithium. To be able to do this, 15 different metal systems were precipitated with these two precipitating agents at 8 and 12 molar equivalent. The samples were then analyzed through ICP-OES, XRD, gravimetric analysis, and SEM-EDX. The results showed that the precipitation efficiency of the transition metals cobalt, nickel and manganese, in all the system was 98% or more. Lithium precipitated only with carbonate. In the system with four metals and 12 molar equivalents carbonate lithium 78% was precipitated. The results indicate that higher concentration of carbonate leads to higher precipitation efficiency. A way to likely reach a higher effective concentration is to first neutralize the solution with sodium hydroxide and then precipitate it with carbonate.

In the design of a solvent extraction plant for metals it is necessary to treat the equilibrium data either graphically or analytically. This enables stagewise calculations to be performed to explore solvent usage and feed conditions and so optimise on the cost of recovery of the metal. The present study reviews the methods of presenting and correlating equilibrium data for solvent extraction systems involving metals; the limitations of each approach are highlighted. The most important example of metal extraction which has been studied falls into that class involving a metal species, in acid aqueous media, which displaces protons from the organic extractant during the mass transfer process. In the typical case of copper extracted by hydroxyoximes the equilibrium problem reduces to one of modelling a surface. The concentration of copper in the organic phase is a function of the concentrations of copper and sulphuric acid in the aqueous phase. Empirical models seem to be as satisfactory to the engineer as chemical ones provided the model is used between restricted regions of data. Practical work has involved the measurement of equilibrium data for the extraction of zinc and copper by di- (2-ethylhexyl) phosphoric acid (D2EHPA) in a kerosene diluent. Both the single and binary metal systems have been studied. The data reported are for feeds between 2-40 g/l zinc, 2-60 g/l copper and 20% V/v D2EHPA. A limited number of results are also presented for 10% V/v D2EHPA. Specific chemical and empirical models have been developed to correlate these data. Because the extractant has a high affinity for zinc in the presence of copper the binary data can be modelled making the assumption that the interaction of copper on zinc is negligible. However the effect of zinc on the limited extraction of copper is significant, the zinc reducing the copper loading markedly. In this way zinc can be decontaminated of copper. The methods for presentation of equilibrium data are discussed and a computer program is given which displays three dimensional equilibrium surfaces. Classical design procedures for stagewise. calculations are used against these three dimensional data plots. Computer programs which allow the investigation of a variety of operating conditions have also been written.

Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2017-06-01T14:05:35Z No. of bitstreams: 1 2015 - Theo Antonio de Jesus.pdf: 3265233 bytes, checksum: 84b1c9854e0877f1a010f74527aca2e5 (MD5) / Made available in DSpace on 2017-06-01T14:05:35Z (GMT). No. of bitstreams: 1 2015 - Theo Antonio de Jesus.pdf: 3265233 bytes, checksum: 84b1c9854e0877f1a010f74527aca2e5 (MD5) Previous issue date: 2015-01-23 / Technological advances encourages the constant exchange of electronic equipment by increasing the amount of waste generated. The concern with the disposal of these wastes is related to the amount of available metals and final disposal, which usually occurs in dumps or landfills. These wastes have precious metals and other trace elements that are released into the environment by leaching from the organic acid attack. Most of these residues has printed circuit boards in which are concentrated the most metals, and the characterization of these plates help to choose the most appropriate recycling processes. This study aimed to characterize the printed circuit boards of mobile phones as its danger and composition as well as preliminarily investigate the possibility of copper recovery via an electrolytic process and test a mixture of coagulant / flocculant in the removal of metals, including copper. The plates were ground knives in order to release the metals and then separating the particle size was made in three fractions of different sizes. Each of the fractions was characterized by digestion in aqua regia, diffraction and X-ray fluorescence characterization, as the danger was performed through recommended by the ABNT NBR 10005. In the fractions resulting from the grain size were performed gravity separations. For the recovery of copper was used in electrolytic technique medium prepared with the electrolyte coming from the gravimetric fraction with a higher concentration of metals. The copper recovery efficiency through electrolytic process was evaluated by the decrease of its concentration in the electrolyte at five different times. Also, the use of coagulant mixture / flocculant had their efficiency assessed by check which proportion coagulant / flocculant used resulted in solution with lower concentrations of metals. It is also made of copper recovery compared by both methods. Mechanical processes are used to promote adequate concentration of most metals with approximately 80% in the coarser fraction using the separation grain size. The characterization results showed that the printed circuit boards of mobile phones are rich in copper, mean values reaching 40%, in addition to having small amounts of gold and silver. In the study of danger, lead levels were found in amounts well above the limit established by ABNT NBR 10004, requiring specific treatments at the disposal of this type of waste. Some proportions coagulant / flocculant used produced better results than others, getting, on average, above 90% removal. The recovery of copper showed better performance using the electrolytic process, compared to that obtained at any ratio coagulant / flocculant used once reached 98.05 % after 40 minutes. It was estimated the average revenue generated in the recovery of metals from the main printed circuit boards of mobile phones discarded in 2013 in Brazil, reaching the amount of US $ 6,182,263.06 / O avan?o tecnol?gico incentiva a troca constante dos equipamentos eletroeletr?nicos aumentando a quantidade de res?duos gerados. A preocupa??o com a disposi??o desses res?duos est? relacionada com a quantidade de metais existentes e sua disposi??o final, que geralmente se d? em lix?es ou aterros. Estes res?duos apresentam metais preciosos e outros elementos tra?os que s?o liberados no meio ambiente pela lixivia??o proveniente do ataque de ?cidos org?nicos. A maior parte destes res?duos possui placas de circuito impresso onde est? concentrada a maior parte dos metais, sendo que a caracteriza??o destas placas ajuda na escolha dos processos de reciclagem mais adequados. Este trabalho teve como objetivo caracterizar as placas de circuito impresso de telefones celulares quanto sua periculosidade e composi??o, bem como investigar preliminarmente a possibilidade de recupera??o de cobre via um processo eletrol?tico e testar uma mistura de coagulante/floculante na remo??o de metais, inclusive cobre. As placas foram processadas em moinho de facas, a fim de liberar os metais e, em seguida, foi feita a separa??o granulom?trica em tr?s fra??es de diferentes tamanhos. Cada uma das fra??es foi caracterizada por digest?o em ?gua r?gia, difra??o e fluoresc?ncia de raios X. A caracteriza??o, quanto ? periculosidade, foi realizada por meio do preconizado pela NBR ABNT 10005. Nas fra??es oriundas da granulometria foram realizadas as separa??es gravim?tricas. Para a recupera??o de cobre foi utilizada a t?cnica eletrol?tica por meio de eletr?lito preparado com a fra??o oriunda da gravimetria com maior concentra??o de metais. A efici?ncia da recupera??o de cobre via processo eletrol?tico foi avaliada por meio da diminui??o de sua concentra??o no eletr?lito em cinco tempos diferentes. J? a utiliza??o da mistura coagulante/floculante teve sua efici?ncia avaliada pela verifica??o de qual propor??o coagulante/floculante utilizada resultou em solu??o com menor concentra??o de metais. Fez-se tamb?m a compara??o de recupera??o de cobre por ambos os m?todos. Os processos mec?nicos utilizados foram adequados para promoverem a concentra??o da maioria dos metais alcan?ando cerca de 80 % na fra??o mais grosseira utilizando-se a separa??o granulom?trica. Os resultados da caracteriza??o mostraram que as placas de circuito impresso de celulares s?o ricas em cobre, alcan?ando valores m?dios de 40 %, al?m de apresentarem pequenas quantidades de ouro e prata. No estudo de periculosidade, foram encontrados n?veis de chumbo em quantidades muito acima do limite estabelecido pela NBR ABNT 10004, sendo necess?rios tratamentos espec?ficos no descarte deste tipo de res?duo. Algumas propor??es de coagulante/floculante utilizadas produziram resultados mais satisfat?rios que outras, ficando, na m?dia, acima dos 90 % de remo??o. A recupera??o de cobre apresentou melhor desempenho utilizando processo eletrol?tico, quando comparado ao obtido a qualquer propor??o de coagulante/floculante utilizada, uma vez que alcan?ou 98,05 % ap?s 40 minutos. Foi estimada a receita m?dia gerada, na recupera??o dos principais metais contidos nas placas de circuito impresso dos telefones celulares, descartados em 2013, no Brasil, chegando-se ao valor de US $ 6.182.263,06.

Shredder fines are the materials with a particle size of less than 10 mm resulting from the shredding of vehicles and complex metal scrap from industries and municipalities. This waste is currently used as landfill construction material, but Stena Recycling wanted to know whether the bottom ash from the combustion of this waste could be useful to the cement industry, and whether it would be feasible to extract Cu and Zn from this ash. To determine this the shredder fines were combusted, and the generated bottom ash underwent chemical fractionation. The leachates from this were processed using MP-AES to obtain an elemental analysis of the ash. The uncombusted shredder fines had its moisture content and calorific value determined. The shredder fines had a moisture content of approximately 11%wt. Due to the heterogeneity of the shredder fines the calorific values varied significantly across the tested samples. The average value was 7.8 MJ/kg. The chemical fractionation showed that the elements in the ash are mostly insoluble in water and ammonium acetate, as the majority remained in the solid residue. This indicates that the ash is inert, and not susceptible to heavy metal leaching. The elemental analysis showed that there is a significant amount of Fe in the ash, with reasonable amounts of Cu and Zn. This project concluded that without additional processing the ash would not be suitable for the cement industry, and that there is potential for the recovery of Cu and Zn from the ash.

Metals, essential constituents of a vast number of products and industrial processes, are paradoxically confronted to a scarcity issue without precedents. Among the emerging technologies for sustainable metal recovery, bio-electrochemical systems (BES) stand at a research state with a potential application on low-content metal streams. They are based on electroactive bacteria that can exchange electrons with their environment to drive an (electro)chemical metal precipitation. The feasibility of three configurations of BES aiming to recover metals at low-energy and low-chemicals consumption was explored. A first approach inspired on metal-bacteria interactions aimed to transform gold and chromium ions into added-value products. A polarized cathode promoting the metal reduction and symbiotically producing metallic nanoparticles on bacteria was studied. A second configuration used a halophilic bioanode to recover a panel of metals including transition metals and rare earth elements from marine environments. Metals were not directly precipitated by the contact with bacteria, but via a gas-diffusion cathode coupled to the bioanode. The third configuration considered a neodymium electrochemical reduction coupled to an oxidation catalyzed by a bioanode. Here, the conventional metal-containing aqueous system was replaced by an ionic liquid, an emerging solvent suitable for REE electrodeposition. / Les métaux, composants essentiels d'un grand nombre de produits et de processus industriels, sont paradoxalement confrontés à un problème de pénurie sans précédent. Parmi les technologies émergentes pour la récupération durable des métaux, les systèmes bio-électrochimiques (BES) sont à la recherche d’une application potentielle sur des matrices aqueuses de métaux à faible teneur. Ils sont basés sur des bactéries dites électro-actives, pouvant échanger des électrons avec leur environnement afin de conduire une précipitation de (électro)chimique du métal. Le but étant d’explorer différents procédés de récupération de métaux à faible consommation d'énergie et de produits chimiques, trois configurations de BES ont été abordés. Une première approche inspirée des interactions métal-bactérie visait à transformer les ions d’or et de chrome en produits à valeur ajoutée. Une cathode polarisée favorisant la réduction des métaux et produisant de manière symbiotique des nanoparticules métalliques sur des bactéries a été étudiée. Une seconde configuration utilisait une bioanode halophile pour récupérer un panel de métaux comprenant des métaux de transition et des éléments de terres rares provenant d’environnements marins. Les métaux ne sont pas précipités directement par le contact avec les bactéries mais par une cathode à diffusion gazeuse couplée à la bioanode. La troisième configuration envisageait une réduction électrochimique au néodyme couplée à une oxydation catalysée par une bioanode. Le système aqueux contenant un métal conventionnel a été remplacé par un liquide ionique, un solvant émergent avantageux pour l'électrodéposition de terres rares.

Den pågående elektrifieringen av transport och samhälle kräver utveckling av nya metoder för återvinning av batterier. Hydrometallurgi som fokuserar på selektiv kristallisation av metaller är ett intressant alternativ för dessa ändamål. Dessa system kan studeras genom modellering och simulering. Många matematiska modeller finns tillgängliga för att beskriva de olika involverade processerna i kristallisationen av metaller. Dessa processer inkluderar övermättnad, nukleation, kristalltillväxt och aggregation. Denna rapport sammanställer ett antal av de tillgängliga matematiska modellerna och presenterar ett numeriskt tillvägagångssätt för modellering av den tidsberoende nummerdensiteten av partiklar genom en populationsbalansekvation. Populationsbalansen kan lösas med olika metoder såsom momentmetoden och metoden av viktade residualer. Här löses ekvationen genom diskretisering. Diskretisering av den inre koordinaten i ett flertal längdintervall möjliggör simulering av partikel-storleksfördelningen som en funktion av tid. Det numeriska tillvägagångssättet applicerades på bariumsulfatutfällning i en perfekt blandad satsreaktor och två- och tre-dimensionella T-mixer-system, såväl som en perfekt blandad satsreaktor för förträngningskristallisation av nickelsulfat med groddning. Den simulerade storleksfördelningens placering visade sig ha bra överenstämmelse med experimentell data vid låga Reynolds-tal. Här undersöktes även påverkan av en mängd parametrar såsom diskretisering, aggregation och magnituden av diffusion. Aggregation hade en märkbar inverkan på välblandade system. Inverkan av aggregation i diffusions-kontrollerade system med kort retentionstid var låg. Diffusionsmagnituden hade liten påverkan på den normaliserade distributionen men större på det totala antalet partiklar. / The currently ongoing electrification of society and transport necessitates the development of novel methods for battery recycling. Hydrometallurgy with a focus on selective metal crystallisation is an interesting prospect to these ends. The resource recovery systems of interest can be studied through simulation where many mathematical models are available to describe the varying processes involved. These processes include supersaturation generation, nucleation, growth and aggregation. This work compiles some of these mathematical models and presents a numerical approach for the modelling of the time-dependent particle number density with a population balance equation. The population balance equation can be solved using a variety of different methods such as method of moments and method of weighted residuals. Here, the balance equation was solved by discretisation. Discretising the inner coordinate (crystal length) into a number of length intervals allows for the particle size distribution to be modelled as a function of time for various crystallisation systems. The framework was successfully applied to barium sulphate precipitation in a perfectly mixed batch reactor and two- and three-dimensional T-mixer systems, as well as a seeded perfectly mixed nickel sulphate anti-solvent crystallisation system. The simulated size distribution showed promising similarity to experimental data at low Reynolds number. The influence of a variety of parameters such as aggregation and magnitude of diffusion was investigated. Aggregation had a significant impact on well-mixed systems increasing with retention time. The impact of aggregation on diffusion-controlled systems with low retention time was low. The magnitude of diffusion had little impact on the particle size distribution of the crystal population but a large impact on the total number of crystals.

The Aurora zone is an ore zone which was recently discovered in the Björkdal gold mine, northern Sweden, and it has been the main focus of mining and exploration activities for the past few years (Pressacco et al., 2020). The purpose of this project is to determine how gold occurs in the Aurora zone. A three-day long campaign was therefore done at the processing plant at the Björkdal mine where 11 000 tonnes of ore from the drive Aurora 370/1650 E+W were processed. The issue regarding the ore from the Aurora zone is that it has a lower recovery compared to the rest of the mine.  Six chip samples, 12 samples from the ingoing plant feed and two tailing samples were analyzed using optical microscopy, scanning electron microscopy (SEM), and automated mineralogy (QEMSCAN). This was done to determine the mineralogy, grain size distribution, mineral associations, textures and modal mineralogy which all are factors that could influence the metal recovery at the processing plant. The samples were prepared using the cold mounting method and epoxy mounts were created. After cutting, grinding, and polishing, the sections were ready to be examined. Optical microscopy was performed using a Nikon ECLIPSE E600 POL microscope. Ten epoxy mounts were carbon coated and automated mineralogy was performed on nine of them in a ZEISS Sigma 300 VP using a recipe (analysis mode) for “bright phase search”. Manual point-ID analysis was done using a ZEISS MERLIN SEM. Fifty gold grains were identified in this study, 48 of them in the chip samples and two of them in the ingoing-feed samples. 64% of them were associated with silicates, 22% were quartz associated, 12% were associated with bismuth minerals and 2% of them were associated with sulfides. The grain size distribution has a range between 0.7 and 19 μm and the median grain size is 4.8 μm. The gold grains identified from the Aurora zone have a significantly smaller median grain size than gold from other parts of the mine. The majority of the gold grains identified in this study, have a very fine grain size, are mainly associated with silicates and most prominently occur as inclusions. Gold that occurs in this way is typically difficult to recover in the processing plant and it seems like this is the main reason for the lower gold recovery from the Aurora ore zone.  No gold was found in the tailings, suggesting that the mineral process is performing well although no thorough conclusion can be made in regards of the processing. The lack of data for the different sample types in this project is an issue. Gold from the tailings must be identified and examined to draw any clear conclusions regarding the processing. For future work, it is therefore recommended to analyze more tailing samples and to implement hydroseparation at the sample preparation stage, to separate the heavier gold particles from lighter minerals. Then more gold will most likely get detected in the tailing samples.

Thesis (M. Tech.(Chemistry)--Vaal University of Technology)), 2010 / Mining industry produces metals which are economical and serve as high valuable commodities in South Africa. This country is regarded as the world leading producer of precious metals such as platinum group metals (PGMs). Silver (Ag), which is also a precious metal, contribute to the country’s economy wealth due to its significance during industrial applications. Base metals such as copper (Cu) and nickel (Ni), though they are low valued, play a significant role in the republics economic wealth. Mining wastewater contains some of these metals, which end up polluting the environment. A possibility to recover this was investigated using NF membranes. Mine effluent was simulated by using relevant reagents. Characterization of NF90, NF- and NF270 membranes, was done by using scanning electron microscopy (SEM), clean water permeability, single charged salts of NaCl and MgCl2 and binary mixture of NaCl/MgCl2 studies. All the rejection experiments were conducted at pH 2.0 with varying pressure and concentrations. Flux measurements indicated that water permeability through the membranes trend, NF270 > NF90 > NF-. The experiments were performed at pressures of 5 bar, 10 bar, 15 bar and 20 bar. For NF90 membrane, a rejection of Na+ monovalent ion in 20 ppm solution was less than of Mg2+ (divalent) ion. Percentage rejections of 90% (Na+) and 98% (Mg2+) were achieved. NF- had rejection of 83% and 90% for Na+ and Mg2+, respectively. In the case of NF270, the membrane had rejection of 92% (Na+) and 94% (Mg2+), respectively. At 100 ppm, all three membranes showed a decreasing trend in rejection while increasing pressure. For binary-solution mixture, Mg2+ ion still had the highest rejection compared to Na+ ion with about 94% and 85% on NF90 than on NF270 and NF-. The high rejection of divalent ion as compared to monovalent ion for charged solutes was due to solute size and electrostatic interaction between the membrane surface layer and the solute. In the case of transition metal rejection studies, Pd2+ ion had an average of 90%, with Ni2+ ion ≈ 95% and Cu2+ ion ≈ 98% as single salts on NF90 compared to NF270 and NF-. However, as for binary and trinary solution mixture, the competition amongst ions was high, where Pd2+ ion rejection was ≈ 99,0%, while Ni2+ and Cu2+ ions was > 90% on NF90 and NF-. Therefore it was excluded from the tests. For the monovalent metal ions (Ag+ and Cu+), the rejection was > 90% in almost all concentrations mixtures. During membrane fouling evaluation, AgCl salt fouled the most, compared to other metal ions, forming a concentration polarization accumulation on the membrane surface for both 20 and 100 ppm solutions. This situation leads to cake layer formation which causes a flux decline, reduces membrane life time and lowers the rejection performance of NF membranes. The aim of this study was to evaluate the performance of three commercial polymeric membranes (NF90, NF270 and NF-) during rejection of the metal